In chain transmissions, it is common to use a roller chain, a rollerless bushing chain, or a silent chain. Furthermore, hybrid chains in which the features of a silent chain and the features of a roller chain or bushing chain are combined have been used in a chain transmission.
A typical chain transmission incorporating such a hybrid chain is shown in FIGS. 15 and 16. In FIG. 15, a chain 510 comprises link plates 511, which function as a silent chain. Link plates 511, each of which has a pair of teeth are disposed along both sides of the chain in alternating, overlapping, relationship. Link plates 512, which do not have teeth, are disposed in alternating, overlapping, relationship along the inside of the chain, and cooperate with rollers 520 in such a way as to function as a roller chain. The link plates 511 and 512 are connected by connecting pins 530. A sprocket 550, shown in FIG. 16, has teeth 552, which cooperate with the teeth of plates 511, and teeth 551, which cooperate with the rollers 520.
In the operation of the chain transmission, teeth of the link plates 511, which function as a silent chain, engage sprocket teeth 552. When a tooth of a link plate 511 is seated on a sprocket tooth 552, a roller 520 engages a sprocket tooth 551. Further details of the chain transmission just described can be found in Japanese Examined Patent Publication No. Sho. 59-30936.
A chain transmission using a convention silent chain exhibits significant elongation due to wear of its connecting pins, and the elongation of the chain is accompanied by a reduction in its strength. In a chain transmission using a conventional roller chain, obtaining high strength is difficult, especially because of difficulties in strengthening the rollers. Furthermore, conventional roller chains produce a large amount of noise as they come into engagement with a sprocket.
In the hybrid chain describe above, in which the outer link plates function as a silent chain, the problem of elongation due to wear of the connecting pins has not been overcome. Thus, as in the case of a conventional silent chain, elongation of the chain occurs, and is accompanied by a decrease in strength.
Another problem with the hybrid chain is that, because it has a total of eight plates in the direction of the chain width, and various different components, assembly of the chain is complicated.
This invention addresses the above-described problems by providing a chain transmission in which engagement noise is reduced, in which a decrease in chain strength due to elongation resulting from excessive wear of the connecting pins is avoided, and the number of different components is relatively small so that assembly of the chain is made easier.